A Fatigue Life Assessment of Automotive Coil Spring and Lower Arm Due to Road Surface Contours

This study aims to determine the effect of road surface contours on the life of car suspension components. In this study, strain gauges were fixed on the critical points of a coil spring and a lower arm. The car went through smooth and rough road surfaces with speeds over 30 and below 20 km/h, respectively, for 60 s. The strain signals obtained were analyzed according to the Coffin-Manson, Morrow and Smith–Watson–Topper models. According to the strain amplitudes measured, the coil spring fatigue life of the rough road surface was 16% lower compared with the smooth surface, whereas the lower arm of the rough road surface was 27% lower than the smooth surface. It was also found that the coil spring failed 36% faster than the lower arm when driving on the rough road surface. This is because the contour of the surfaces provides a vertical load affecting the coil spring at higher rates than the lower arm. It is in accordance with the function of the coil spring which works to reduce the load vertically.